/**
 * 给你一个字符串 s ，将该字符串中的大写字母转换成相同的小写字母，返回新的字符串
 */
public class Main {
    public static String toLowerCase(String s) {
        if(s == null||s.length() == 0){
            return null;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if(ch >='A' && ch<='Z'){
                sb.append((char)(ch+32));
            }else {
                sb.append(ch);
            }

        }
        return sb.toString();
    }

    public static void main(String[] args) {
        String s = new String("Hallo World");
        String ret = toLowerCase(s);
        System.out.println(ret.toString());
    }
}